Organic reagents for removing heavy metals from a 10-34-0 (N-P2O5-K2O) grade fertilizer solution and wet-process phosphoric acid

Fertilizer solutions and wet-process phosphoric acid (WPA) contain heavy metal impurities such as cadmium, zinc, lead, copper, manganese, and chromium. Trisodium trithiocyanuric acid (TMT-15), sodium trithiocarbonate (5% Na₂CS₃), and sodium polythiocarbonate (Thio-Red II) were evaluated as precipitating agents for heavy metals in a 10-34-0 (N-P₂O₅-K₂O) grade fertilizer solution and WPA. A water-insoluble starch xanthate was also evaluated as an adsorbent for the heavy metals in 10-34-0 (N-P₂O₅-K₂O) and WPA. Arsenic (24–99+%), cadmium (36–97+%), copper (98+%), mercury (96+%), lead (83–88+%), and zinc (8–83+%) precipitated from 10-34-0 (N-P₂O₅-K₂O) upon the addition of each organic reagent, while levels of manganese and chromium were unaffected. Mercury (97+%), lead (75+%), cadmium (11–38%), copper (99+%), and chromium (3–35%) precipitated from WPA upon the addition of 5% Na₂CS₃ and Thio-Red II, while precipitation of manganese and zinc was negligible. The water-insoluble starch xanthate adsorbed mercury (96+%), copper (38–98+%), and lead (24–75%) from 10-34-0 (N-P₂O₅-K₂O) and WPA while adsorption of arsenic, cadmium, manganese, chromium, and zinc was negligible.     

Special features of synthesis of a heat-resistant glass-ceramic coating

In order to protect Ni–Cr alloys from high-temperature corrosion, a new heat-resistant glass-ceramic coating was developed with a glass matrix synthesized on the basis of a composite R _x O–Al₂O₃–SiO₂–TiO₂ (R–Li^–, Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺) system. The special features of the formation of crystalline phases in the glasses in heat treatment and the optimum regime for the formation of a glass ceramic structure are described.Translated from Steklo i Keramika, No. 3, pp. 30–32, March, 1996.     

<Emphasis Type="Italic">In situ</Emphasis> microobservation of the cathode in molten carbonate fuel cells

In molten carbonate fuel cells (MCFC), the wettability of the electrode and the electrolyte distribution are very important factors influencing the active reaction area. We have observed the molten carbonate behaviour directly on the cathode (porous NiO) and the electrolyte plate (LiAlO₂) under various gas conditions and at controlled potentials using an environmental scanning electron microscope (ESEM) equipped with a hot stage. We estimated the liquid electrolyte distribution in the cathode and measured the contact angles on NiO and LiAlO₂ in the electrolyte. Moreover, the electrolyte movement in the reaction CO₂ + O₂ + 2e^– = CO₃ ^2– was observed on the surface of the porous NiO in a CO₂/O₂ atmosphere. The reaction CO₃ ^2– + 2e^– = CO + 2 O^2– of the gas generation was observed in a H₂O atmosphere. The active reaction points on the electrode are the areas where the electrolyte film is thin.     

Thermomechanical properties of ceramics in the systems Al2O3-TiO2 and Al2O3-TiO2-mullite

Conclusions We studied certain properties of ceramics in the systems Al₂O₃-TiO₂ and Al₂O₃-TiO₂-mullite, obtained by the use of the double-stage synthesis of aluminum titanate.We established the nature of the change in the high-temperature strength in relation to the ratio of Al₂O₃ and aluminum titanate. The maximum high-temperature strength (bending) at 1200°C is possessed by ceramic with a corundum matrix and a volume proportion of aluminum titanate equal to 40–45%.It is established that the addition of CaO + SiO₂ made in amounts of up to 1.0–1.5% contributes to the partial breakdown of the aluminum titanate in the compositions Al₂O₃-TiO₂ and the production of a ceramic with a bending strength of 160–190 N/mm² at 20–200°C, thermal-shock resistance 650–800°C, and thermal conductivity of 1.9–2.1 W/(m·K).We studied the effect of the mullite concentration on the properties of the ceramic in the system Al₂O₃-TiO₂-mullite. The introduction of mullite in amounts of not more than 50%, containing up to 3% of impurities, contributes to an increase in the ceramic's strength in the range 20–1300°C and in the thermal shock resistance.Translated from Ogneupory No. 2, pp. 22–26, February, 1988.     

The Electro-Reduction of Carbon Dioxide in a Continuous Reactor

This paper reports an investigation into the electro-reduction of CO₂ in a laboratory bench-scale continuous reactor with co-current flow of reactant gas and catholyte liquid through a flow-by 3D cathode of 30^# mesh tinned-copper. Factorial and parametric experiments were carried out in this apparatus with the variables: current (1–8 A), gas phase CO₂ concentration (16–100 vol%) and operating time (10–180 min), using a cathode feed of [CO₂ + N₂] gas and 0.45 m KHCO₃(aq) with an anolyte feed of 1 m KOH(aq), in operation near ambient conditions (ca. 115 kPa(abs), 300 K). The primary and secondary reactions here were respectively the reduction of CO₂ to formate (HCOO⁻) and of water to hydrogen, while up to ca. 5% of the current went to production of CO, CH₄ and C₂H₄. The current efficiency for formate depended on the current density and CO₂ pressure, coupled with the hydrogen over-potential plus mass transfer capacity of the cathode, and decreased with operating time, as tin was lost from the cathode surface. For superficial current densities ranging from 0.22 to 1.78 kA m⁻², the measured values of the performance indicators are: current efficiency for HCOO⁻ = 86–13%, reactor voltage = 3–6 Volt, specific energy for HCOO⁻ = 300–1300 kWh kmol⁻¹, space-time yield of HCOO⁻ = 2 × 10⁻⁴–6 × 10⁻⁴ kmol m⁻³ s⁻¹, conversion of CO₂ = 20–80% and yield of organic products from CO₂ = 6–17%.     

Anthropogenic emissions of NOX, NH3 and N2O in India

Emissions of NO_x, NH₃ and N₂O from anthropogenic activities in India have been estimated based on actual field measurements as well as available default methodologies. The NO_x emissions are mainly from the transport sector and contribute about 5% of the global NO_x emission from fossil fuel. NH₃ emissions from urea seems to be highly uncertain. However, emissions of NH₃ from fertilizers and livestock are estimated to be 1175 Gg and 1433 Gg, respectively. N₂O emissions seem to be derived predominantly from fertilizer applications, resulting in the release of 199–279 Gg N₂O. Other sources of N₂O, viz. agricultural residue burning, biomass burning for energy and nitric acid production are estimated to be 3, 35–187 and 2–7 Gg, respectively.     

Explosive Hazard of Vapor–Gas Mixtures of Fluoride‐Containing Saturated Hydrocarbons with Fluoride and Chlorine Trifluoride

The limits of explosion of the CF₃CFH₂–F₂–N₂, C₃F₈–F₂–N₂, C₄F₈–F₂–N₂, C₄F₈–ClF₃–N₂, C₄F₁₀–ClF₃–N₂, and F₂ClCF₂Cl–F₂–N₂ mixtures are determined. For some compositions of the first two mixtures, the maximum pressure of explosion and the maximum pressuregrowth rate are measured. The transition from deflagration to detonation is observed in undiluted mixtures close to stoichiometric compositions. The burning rates of the mixtures examined are comparable with the burning rates of oxygen–hydrogen mixtures.     

The positive effect of hydrogen on the reaction of nitric oxide with carbon monoxide over platinum and rhodium catalysts

The effect of adding 330–4930 ppm hydrogen to a reaction mixture of NO and CO (2000 ppm each) over platinum and rhodium catalysts has been investigated at temperatures around 200–250°C. Hydrogen causes large increases in the conversion of NO and, surprisingly, also of CO. Oxygen atoms from the additional NO converted are eventually combined with CO to give CO₂ rather than react with hydrogen to form water. This reaction is described by CO + NO +3/2H₂ CO₂ + NH₃ and accounts for 50–100% of the CO₂ formed with Pt/Al₂O₃ and 20–50% with Rh/Al₂O₃. With the latter catalyst a substantial amount of NO converted produces nitrous oxide. Comparison with a known study of unsupported noble metals suggests that isocyanic acid (HNCO) might be an important intermediate in a reaction system with NO, CO and H₂ present.     

Synthesis of graft copolymers of polycaprolactam fibre by preliminary introduction of hydroperoxide groups

Conclusions 1. We have obtained graft copolymers of polycaprolactam fibre with various vinyl monomers by introducing peroxide and hydroperoxide groups into the fibre by oxidation with an Fe³⁺-H₂O₂ system.2. We have studied the effect of the oxidation and graft copolymerisation conditions on the yield of graft copolymer. The feasbility of obtaining modified polycaprolactam fibre with practically any content of graft polymer has been demonstrated.All-Union Correspondence Institute for the Textile and Light Industry (VZITLP); Moscow Textile Institute. Translated from Khimicheskie Volokna, No. 6, pp. 15–17, November–December, 1969.     

Combustion of a Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-TiO<Subscript>2</Subscript>-Al-C Powder Mixture in the SHS Regime and the Structure of the Combustion Products

The combustion of pressed specimens of a stoichiometric Fe₂O₃-TiO₂-Al-C powder mixture burning in the SHS regime is studied. It is found that the final product has the same shape and size as the initial specimen. The composition and structure of the final product, which is highly porous high-melting Al₂O₃-TiC-Fe(Ti) composite ceramics, are studied. The mechanism of phase and structure formation in the examined system is proposed.__________Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 4, pp. 60–66, July–August, 2005.     

Kinetics and Mechanism of the Interaction of Alkali Calcium Silicate Glasses with Salt Melts in the KNO3–Pb(NO3)2 System

The interaction of alkali calcium silicate glasses with salt melts in the KNO₃–Pb(NO₃)₂ system is investigated at temperatures of 420–520°C. The chemical composition of crystalline coatings formed upon treatment contains both components of the initial glass (SiO₂, 9–12 wt %; CaO, 0.8–1.2 wt %) and components of the salt melt (PbO, 82–89 wt %). The treatment temperature is the main factor affecting the structure of the modified surface layer. The mechanism of the interaction of alkali calcium silicate glasses with salt melts is analyzed. According to this mechanism, the interaction involves the ion exchange (with the participation of Na⁺, K⁺, Ca²⁺, and Pb²⁺ ions), crystallization of modified surface layers, and incorporation of Pb _x O _y nanoparticles (formed in the salt melt) into the coating structure.     

Sintering and some properties of compositions in the Al2O3-Al2TiO5 system with additions of amorphous silica

Conclusions We studied the effect of addtions of amorphous silica in amounts of 6–11% on the properties of compositions in the Al₂O₃-Al₂TiO₅ system.The presence of SiO₂ enables us to obtain, at reduced firing temperatures (1580°C), adequately dense (P_open=3–4%) compositions while preserving the high thermal-shock resistance and compressive strength at 1050°C (360–420 MPa).Translated from Ogneupory, No. 8, pp. 19–20, August, 1986.     

Aspects of making a superconducting yttrium ceramic by self-propagating high-temperature synthesis

Macrokinjetic features are considered for the combustion in oxygen of BaO₂–Cu–Y₂O₃ mixtures, which produces the high-temperature superconductor yttrium barium cuprate YBa₂Cu₃O_7–x. Studies have been made on how the initial temperature affects the combustion temperature and rate, and the critical temperature for self-ignition has been determined. Ultrasonic activation of the initial powders has an advantageous effect on the product quality. Thermal analysis has been applied to the activated mixtures, which indicates the reason for the rise in burning wave propagation rate and increase in conversion to the superconducting phase.Chernogolovka. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 2, pp. 62–67, March–April, 1993.     

Impact of dissolved organic carbon on the determination of trace concentration of Pu-239+240 in the groundwater

Influence of dissolved organic carbon (DOC) on the quantitative estimation of Pu-239+240 in the groundwater was investigated. Impact of DOC in the range of 5–30 ppm was studied in solutions which were directly taken from different wells, whereas to conduct the experiment at the elevated level of DOC, i.e. in the range of 27–60 ppm, groundwater was spiked with stock solution of humic acid (HA), a high molecular weight organic compound. Samples with varying concentrations of DOC were artificially contaminated with a pre-calibrated solution of Pu-239+240 in the laboratory in the range of 200 μBq–17 Bq l^–1, and the pH was controlled at 7.4. Quantitative estimation of plutonium was carried out by pre-concentrating it with Fe(OH)₃. This purified plutonium from Ca²⁺, Mg²⁺ and amphoteric elements. The percentage recovery of Pu-239+240 was 90–92% in the solution having DOC 10 ppm, whereas in samples with DOC in the range of 10–60 ppm, the recovery was 42–43%. Therefore, to improve the recovery of plutonium in the case of the elevated level of DOC, a modified procedure for its quantitative estimation was adopted. In this procedure, after filtration the samples were refluxed with conc. HNO₃ and H₂O₂ to destroy the DOC before pre-concentrating Pu with Fe(OH)₃. By this modified procedure, the average recovery of plutonium at high concentrations of DOC was improved to 90–95%.     

Glass Formation and Luminescence of Glasses in the Ga2S3–GeS2–Nd2S3System

The results of spectral measurements and the differential thermal analysis (DTA) data for glasses in the Ga₂S₃–GeS₂–Nd₂S₃system are presented. The boundaries of the glass formation region in the Ga₂S₃–GeS₂–Nd₂S₃system are determined. It is shown that the luminescence efficiency increases with an increase in the gallium sulfide content due to the displacement of the concentration quenching boundary of Nd³⁺luminescence with a change in the glass matrix composition.     

Uptake of heavy metal ions from aqueous solution using Mg–Al layered double hydroxides intercalated with citrate, malate, and tartrate

Mg–Al layered double hydroxide (Mg–Al LDH) was modified with organic acid anions using a coprecipitation technique, and the uptake of heavy metal ions from aqueous solution by the Mg–Al LDH was studied. Citrate·Mg–Al LDH, malate·Mg–Al LDH, or tartrate·Mg–Al LDH, which had citrate³⁻ (C₆H₅O₇³⁻), malate²⁻ (C₄H₄O₅²⁻), or tartrate²⁻ (C₄H₄O₆²⁻) anions intercalated in the interlayer, was prepared by dropwise addition of a mixed aqueous solution of Mg(NO₃)₂ and Al(NO₃)₃ to a citrate, malate, or tartrate solution at a constant pH of 10.5. These Mg–Al LDHs were found to take up Cu²⁺ and Cd²⁺ rapidly from an aqueous solution at a constant pH of 5.0. This capacity was mainly attributable to the formation of the citrate–metal, malate–metal, and tartrate–metal complexes in the interlayers of the Mg–Al LDHs. The uptake of Cu²⁺ increased in the order malate·Mg–Al LDH < tartrate·Mg–Al LDH < citrate·Mg–Al LDH. The uptake of Cd²⁺ increased in the order malate·Mg–Al LDH < tartrate·Mg–Al LDH = citrate·Mg–Al LDH. These differences in Cu²⁺ and Cd²⁺ uptake were attributable to differences in the stabilities of the citrate–metal, malate–metal, and tartrate–metal complexes. These results indicate that citrate³⁻, malate²⁻, and tartrate²⁻ were adequately active as chelating agents in the interlayers of Mg–Al LDHs.     

Preparation and characterization of TiO2 photocatalysts by Fe doping together with Au deposition for the degradation of organic pollutants

Fe³⁺ doped TiO₂ deposited with Au (Au/Fe–TiO₂) was successfully prepared with an attempt to extend light absorption of TiO₂ into the visible region and reduce the rapid recombination of electrons and holes. The samples were characterized by X-ray diffraction (XRD), N₂ physical adsorption, Raman spectroscopy, atomic absorption flame emission spectroscopy (AAS), UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra. The photocatalytic activities of the samples were evaluated for the degradation of 2,4-chlorophenol in aqueous solutions under visible light (λ > 420 nm) and UV light irradiation. The results of XRD, XPS and high-resolution transmission electron microscopy (HRTEM) analysis indicated that Fe³⁺ substituted for Ti⁴⁺ in the lattice of TiO₂, Au existed as Au⁰ on the surface of the photocatalyst and the mean particle size of Au was 8 nm. Diffuse reflectance measurements showed an extension of light absorption into the visible region for Au/Fe–TiO₂, and PL analysis indicated that the electron–hole recombination rate has been effectively inhibited when Au deposited on the surface of Fe-doped TiO₂. Compared with Fe doped TiO₂ sample and Au deposited TiO₂ sample, the Au/Fe–TiO₂ photocatalyst exhibited excellent visible light and UV light activity and the synergistic effects of Fe³⁺ and Au was responsible for improving the photocatalytic activity.     

Chemically regenerative redox fuel cells II. Regeneration reaction studies

The kinetics of the reduction of TiO²⁺ with H₂ has been studied using a platinum catalyst in hydrochloric acid medium. The kinetic results were used to design the performance of a chemically regenerative redox fuel cell with the Ti³⁺/TiO²⁺ redox couple as anode system. Also the results from another chemically regenerative redox fuel cell with the Fe(EDTA)^2–/Fe(EDTA)^– redox couple as anode system are presented. In both redox cells the VO ₂ ⁺ /VO²⁺ redox couple was used as cathode system.     

Investigation of electroless plating of Ni–W–P alloy films

The electroless deposition of Ni–W–P alloy coatings onto metal substrates using H₂PO₂ ^– as reducing agent from solutions containing nickel sulfate, sodium tungstate, sodium citrate, ammonium sulfate and other additives was studied. At most temperatures (60–80 °C) and pHs (7–11) investigated, bright and coherent coatings uniform in appearance were produced. Phosphorous and tungsten contents ranging from 3.5 to 8 wt % and 0.5 to 6 wt %, respectively, were obtained depending upon solution temperature and pH. Trends such as the effects of pH and temperature on average metal deposition rate and the P content in the alloy are similar to that reported previously for the Ni–P system. Correlation of open-circuit potentials with events occurring at the electrode surface in different solutions and polarization curves provide strong evidence that Ni²⁺ ions participate in W and P deposition, H₂ evolution and H₂PO₂ ^– oxidation and that H₂PO₂ ^– ions participate in cathodic reduction. This indicates that the partial reactions for the Ni–W–P system do not occur independently of one another.     

Redox chemistry of H2S oxidation by the British gas Stretford process part V: Aspects of the process chemistry

Stretford processes use air to oxidize H₂S in process and natural gases to elemental sulphur, by absorption in aqueous solution at about pH 9 and reaction of the resulting HS^– ions with dissolved oxygen, in the presence of anthraquinone disulphonates (AQDS) and vanadium (v) species, which act as catalysts. Kinetic measurements of the reactions (AQ27DS + HS^– ions), (V(v) + HS^– ions) and (AQ27DSH^– + O₂), primarily used stopped flow spectrophotometry, as reported here, following papers on the electrochemical behaviour of the individual redox couples in Stretford Processes. The course of reaction (AQ27DS + HS^– ions) was also followed with a gold bead indicator electrode, the potential of which was determined essentially by the AQ27DS/AQ27DSH^– couple as the former species were reduced to the latter. Attempts to use⁵¹V NMR to characterize aqueous vanadium-sulphur complexes were inconclusive. A possible mechanism for Stretford Processes is postulated, involving polysulphide (S _n ^2–) ions as intermediates, which are oxidized to elemental sulphur by another intermediate, H₂O₂, formed by reaction of AQ27DSH^– ions and dissolved oxygen.